post.rpart {rpart} | R Documentation

## PostScript Presentation Plot of an Rpart Object

### Description

Generates a PostScript presentation plot of an `rpart` object.

### Usage

    post(tree, ...)

    ## S3 method for class 'rpart':
    post(tree, title.,
         filename = paste(deparse(substitute(tree)), ".ps", sep = ""),
         digits = getOption("digits") - 3, pretty = TRUE,
         use.n = TRUE, horizontal = TRUE, ...)

### Arguments

`tree` | fitted model object of class `rpart`. This is assumed to be the result of some function that produces an object with the same named components as that returned by the `rpart` function.
`title.` | a title which appears at the top of the plot. By default, the name of the `rpart` endpoint is printed out.
`filename` | ASCII file to contain the output. By default, the name of the file is the name of the object given by `rpart` (with the suffix `.ps` added). If `filename = ""`, the plot appears on the current graphical device.
`digits` | number of significant digits to include in numerical data.
`pretty` | an integer denoting the extent to which factor levels will be abbreviated in the character strings defining the splits; (0) signifies no abbreviation of levels. A `NULL` signifies using elements of letters to represent the different factor levels. The default (`TRUE`) indicates the maximum possible abbreviation.
`use.n` | Logical. If `TRUE` (default), adds to label (#events level1/ #events level2/etc. for method `class`, `n` for method `anova`, and #events/n for methods `poisson` and `exp`).
`horizontal` | Logical. If `TRUE` (default), plot is horizontal. If `FALSE`, plot appears as landscape.
`...` | other arguments to the `postscript` function.

### Details

The plot created uses the functions `plot.rpart` and `text.rpart` (with the `fancy` option). The settings were chosen because they looked good to us, but other options may be better, depending on the `rpart` object. Users are encouraged to write their own function containing favorite options.

### Side Effects

a plot of `rpart` is created using the `postscript` driver, or the current device if `filename = ""`.

### See Also

`plot.rpart`, `rpart`, `text.rpart`, `abbreviate`

### Examples

    data(car.test.frame)
    z.auto <- rpart(Mileage ~ Weight, car.test.frame)
    post(z.auto, file = "")   # display tree on active device
       # now construct postscript version on file "pretty.ps"
       # with no title
    post(z.auto, file = "pretty.ps", title = " ")
    z.hp <- rpart(Mileage ~ Weight + HP, car.test.frame)
    post(z.hp)

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